@HylandRendering,
Moreover, though it is hard for us to trace the issue without the reproducible case, we are still working on it according to your description. Currently what we can find is that only the formatting feature may cause environment’s CultureInfo being changed. Besides the part which we have fixed for CELLSNET-46781, we found if you implement CustomImplementationFactory.CreateCultureInfo() and returns environment’s default CultureInfo, it also may cause the environment’s CultureInfo being changed. We will provide a fix soon and you may give it a try. For your mentioned “other APIs”, we had thought it is “other libraries/products” of Aspose, such as Aspose.PDF. If so, you may ask help in corresponding forums to get confirmation about the possibility of changing environment’s CultureInfo. If you mean other APIs of Aspose.Cells, we are afraid we cannot find any other features which may cause such kind of issue.